ul{
    width: 800px;
    height: 40px;
    margin: auto;
    display: flex;
    justify-content: space-around;
}
li{
    width: 100px;
    line-height: 40px;
    list-style: none;
    text-decoration: none;
    text-align: center;
}
.on{
    background-color: red;
}
.myul{
    margin-top: 700px;
}